The present invention relates to a method for producing a bondable coating on a carrier strip and to a carrier strip coated with such a method.
In power electronics, copper-based strips are used for the electronic connection of power components with bond wires. It is known from DE 42 29 270 A1 and DE 10 2008 025 664 A1 that bondable coatings can be connected to a carrier strip through rolling. Thus, for example, EP 0 027 520 A1 and U.S. Pat. No. 4,521,257 A recommend the use of copper-tin alloys as carrier materials. The disadvantage of this material is that greater stability of the carrier material and lower costs are desired. More cost-efficient copper-zinc alloys have the disadvantage, however, that they can contaminate the aluminum-based bond layers and bond wires due to their high zinc content, and thus have a negative impact on the connection.
The trend toward increasingly more powerful, copper-based materials in power electronics, which specifically require good relaxation capability and a high degree of stability in addition to good electrical conductivity, is leading to a shift away from bronze materials and toward materials that are capable of excretion. Both with the more low-cost copper-zinc alloys and with other copper-based materials, it was determined that the bond wires can become loose from the bond surfaces, whereby the bond surfaces can break away.
An objective of the present invention is thus to overcome the disadvantages of the prior art. In particular, an objective is to find a method for producing a carrier strip and a carrier strip which meets the standards applicable to carrier strips for high power capacities without an unwanted defect occurring during production or with the electronic components produced using the method. Here, it is necessary, in particular, to avoid a contamination of the bond surface with harmful atoms and a tearing off or damage to the connection of the bond wire to the surface, or between the bond surface and the carrier strip. At the same time, it should be feasible to use the most cost-efficient materials possible as a carrier strip.